| WETyApp : WeakExpr -> WeakType -> WeakExpr
| WECoApp : WeakExpr -> WeakCoercion -> WeakExpr
| WELam : WeakExprVar -> WeakExpr -> WeakExpr
| WETyApp : WeakExpr -> WeakType -> WeakExpr
| WECoApp : WeakExpr -> WeakCoercion -> WeakExpr
| WELam : WeakExprVar -> WeakExpr -> WeakExpr